Generating new antimicrobial agents has, most often, targeted individual organisms. Developing approaches that generate truly broad-spectrum anti-infective agents would be very valuable. One approach to accomplishing this goal would be to develop drugs that enhance the anti-infective efficacy of a host pathway that is active against a wide range of priority organisms. Autophagy and the function of autophagy-related genes {ATG genes) in resistance to infection represent such a pathway. Autophagy and ATG genes have extremely broad protective effects against viruses, bacteria, and parasites and therefore provide unique potential targets for the development of truly broad-spectrum anti-infective agents. Autophagy is a cellular process in which cytoplasmic cargo is captured within a double membrane-bound vesicle for delivery to the lysosome and degradation. We discovered that ATG proteins can also play key roles in host defense via processes that do not require the autophagy pathway. Herein, these mechanisms are called 'ATG gene dependent to distinguish them from 'autophagy-dependent' processes. ATG gene-dependent immunity is important both in vivo and in vitro to protect against infection with the two NIAID priority pathogens. Toxoplasma gondii and norovirus (NoV, a genus of the Caliciviridae). This demonstrates the broad physiologic importance of this novel mechanism of host defense. In Project 3 we will define the mechanisms of ATG gene-dependent immunity, and utilize this information to contribute to the development of broadspectrum anti-infective agents through this CETR program by: (i) participating in a high-density chemical compound screen to stimulate ATG gene-dependent immunity to T. gondii (Project 4, Aim 2), (ii) screening peptides and candidate therapeutics identified in Projects 1 and 4 for activity against T. gondii and both human and murine norovirus (HNoV, MNoV); and (iii) identifying candidate 'mechanism-defined' targets within the ATG gene-dependent immune process for additional chemical compound screens to be performed in Project 4. We will accomplish these goals through the following Specific Aims. AIM 1: Define the molecular mechanisms of ATG protein action \n ATG gene-dependent immunity. AIM 2: Identify proteins and pathways involved In regulating ATG gene-dependent immunity. AIM 3. Determine the physiologic importance of A7G gene-dependent immunity In vivo. AIM 4. Determine the anti-infective potency of genes, autophagy-inducing peptides and candidate therapeutic compounds against NoV and T. gondii.